The present invention relates to apparatus for dissipating impact energy between relatively converging members. A typical environment of usage of such apparatus is a marine environment in which the apparatus is employed to cushion the impact between a marine means (e.g., barge, boat, etc.) and a second structure (e.g., another marine means or a fixed tower, wharf, etc.)
Many forms of protective fender or bumper systems have been proposed, for both onshore and offshore locations, to dissipate kinetic energies imparted, for example, from a floating vessel to a relatively stationary structure such as a mooring or berthing facility. Prior systems have ranged from the simple expedient of worn tire casing nailed to a pier to such highly engineered cushioning systems as the unit described in Dial et al. U.S. Pat. No. 3,864,922 entitled "Sealed Cushioning Unit", issued Feb. 11, 1975. Of course, the desirability of either of these two extremes, or of any of the many other devices proposed, is often determined by both the expense of installation and maintenance and the particular impact situations anticipated in a given environment.
Many suggested cushioning units have included a relatively rigid member for contacting a floating vessel, that member secured to a pier, mooring, etc. through a deformable elastomeric member. The elastomeric member is positioned to be deformed upon impact of the floating vessel with the relatively rigid member, thereby absorbing impact energy. A number of units employing deformable elastomeric members as a cushioning element have provided for shear-type deformation of the elastomeric element as part of the suchioning strategy. Examples of such units can be found in the following references: Wanneroy U.S Pat. No. 3,457,729; Slemmons U.S. Pat. No. 3,055,182; Shirvany U.S. Pat. No. 3,763,653; Hein U.S. Pat. No. 3,235,244; Kinneman U.S. Pat. No. 2,655,005; and a publication of Regal Tool & Rubber Co., Inc., Box 1723 Corsicana Tex., entitled "Barge and Boat Bumpers for Offshore Platforms".
Other units have included the proposal of multiple, horizontally-spaced shock absorbing supports for a single frameline member disposed to contact the floating vessel. Such arrangements can be found in: VonBose et al. U.S. Pat. No. 3,933,111; Tummers et al. U.S. Pat. No. 3,890,916; and Kevar U.S. Pat. No. 3,953,084. Depending upon the particular design features, some such units permit the framelike member to tilt in various orientations in response to forces imparted by a floating vessel, rather than being limited to motion toward, and away from, the wharf to which the shock absorbing units are attached.
Despite the number and variety of previous cushioning unit proposals, unresolved problems have remained, particularly as concerns quite large size suchioning units needed to protect easily damaged marine structures from impact by large, oceangoing barges and boats. Thus, for example, while frame-type units may be desirable to span the distance between spaced apart supports of a marine structure (e.g., the "legs" of an offshore tower), as the scale of the apparatus increases the problem of supporting the vertical weight of such a frame, while still permitting horizontal deflection to be absorbed by shock absorbing units, becomes increasingly vexatious. Additionally, the rupturing of a shock absorbing unit (e.g., owing to wear over a long period of time, sudden excessive loading, etc.), could result in a major components of such a large-scale cushioning unit damaging the structure to which it is affixed, dropping to the body of water, and rendering repair difficult and/or hazardous.